Asphaltic sheet materials are widely used in the construction industry. For example, polymer-modified asphaltic sheet material is used as membrane for waterproofing flat or low-sloped roofs. As is known in the art, these roofing systems may include multiple layers of asphaltic sheet including base sheets and cap sheets. Other examples include barriers materials such air, vapor, or moisture barriers. These materials are typically used on roofs or vertical surfaces such as walls to provide the desired air, vapor and/or moisture resistance to a structure. Still other examples include underlayments, which are used in the roofing industry to provide an extra layer of protection to the roof. This additional protection may provide, among other benefits, water or moisture, thermal, and fire resistance. As the name implies, underlayment is typically positioned below the external or primary roofing protection, which may include shingles, membranes such as polymeric or asphaltic membrane, roofing tiles, and metal panels or cladding.
With regard to underlayments, felt paper that is saturated with asphalt has historically been used as underlayment to provide additional water and/or moisture resistance to the roof. Other forms of underlayment include synthetic materials such as thermoplastic or thermoset materials formed into sheets. Composites, such as laminates of asphalt and synthetic polymer, have also been employed as underlayment.
In order to meet certain fire resistance properties, which may be required by code or classification, fire or flame resistant underlayment may be employed. These underlayment may include textiles, including woven and non-woven fabrics, made of fire resistant materials such as fiberglass. These fabrics may include a coating, such as a mineral coating, that further enhances the flame or fire resistance of the underlayment.
Where there is a desire to achieve both moisture resistance and flame or fire resistance through the use of underlayment, such as with metal roofing systems, multiple underlayments are used. For example, a first underlayment may be used to provide moisture or water resistance, and a second underlayment may be used to provide flame or fire resistance. This technique, however, suffers from several drawbacks including the added difficulty of installing multiple underlayments.